The present invention relates to power saving in a storage system.
For example, a remote copying technique disclosed in Japanese Unexamined Patent Application Publication 2005-18506 is known. In Japanese Unexamined Patent Application Publication 2005-18506, a first storage system receives a data element transmitted from an upper order device, creates a journal including the data element, which is written in a primary logical volume, and transmits the journal to a second storage system. The second storage system receives the journal from the first storage system, and writes the received journal in a journal storage area. The second storage system writes data elements included in accumulated journals in the journal storage area to a secondary logical volume. By means of this series of processes, a copy of the data in the primary logical volume is generated in the secondary logical volume.
Further, power saving techniques disclosed in Japanese Unexamined Patent Application Publication 2000-293314 and Japanese Unexamined Patent Application Publication 2005-157710 are known. According to Japanese Unexamined Patent Application Publication 2000-293314, when a fixed time period elapses following the end of access from an upper order device, a storage system performs a power saving operation to shift the non-accessed storage device to a power saving mode or switch the power of the storage device OFF. According to Japanese Unexamined Patent Application Publication 2005-157710, a storage system cuts the power of a storage device in response to an instruction from an upper order device when the upper order device has no intention of accessing the storage device for a certain time period.
When an attempt is made to reduce the power consumption of a storage system in remote copying technology, power saving in the first storage system can be achieved using the power saving technique described in Japanese Unexamined Patent Application Publication 2000-293314 or Japanese Unexamined Patent Application Publication 2005-157710, for example. The reason for this is that in Japanese Unexamined Patent Application Publication 2000-293314 and Japanese Unexamined Patent Application Publication 2005-157710, the power consumption of the storage device is reduced on the basis of access or a command from the upper order device, and in remote copying technology, the primary logical volume in the first storage system typically serves as the access destination of the upper order device.
From this viewpoint, however, the power saving techniques disclosed in Japanese Unexamined Patent Application Publication 2000-293314 and Japanese Unexamined Patent Application Publication 2005-157710 cannot be applied easily to the second storage system. The reason for this is that unlike the primary logical volume, the secondary logical volume in the second storage system does not usually serve as an access destination of the upper order device, and moreover, the remote copying disclosed in Japanese Unexamined Patent Application Publication 2005-18506 is so-called asynchronous remote copy, or more specifically remote copying that is executed asynchronously in relation to access to the primary logical volume by the upper order device.